Non-invasive detection of a deeply buried two-dimensional electron gas at the LaFeO3/SrTiO3 interface via Giant top interdigital capacitance

• LaFeO3 thin films epitaxially grown on untreated single crystal SrTiO3 substrates. • Probing the existence of a two-dimensional electron gas (2DEG) at the interface. • Non-invasive detection of a buried 2DEG by remote surface capacitance measurements. • Tailoring the interfaces between different crystalline materials at atomic scale. In this study, we investigate the properties of LaFeO 3 thin films epitaxially grown on untreated single crystal SrTiO 3 substrates and propose a new method of detecting the deeply buried conductive interface of the crystalline LaFeO 3 /SrTiO 3 heterostructure, by using remote capacitance measurements via interdigital electrodes deposited on the top surface. To the best of our knowledge, this is the first non-invasive detection of a buried two-dimensional electron gas (2DEG) using top capacitance measurements in this configuration. Moreover, the 2DEG is detected at a crystalline polar-nonpolar interface on untreated SrTiO 3 substrates, with previous studies mostly focusing on treated substrates. The huge planar top capacitance, linked to the presence of a 2DEG at the bottom interface, could be further modulated and could open the way to novel device applications.